First seller financing BRRRR deal - Please critique

[Bridget Campbell]

Please help BP community!

Single family vacation home

The purchase price offered is $675,000

Down payment amount is $33,750 (5%)

Financed amount at closing $641,250

Interest rate is 3%

Balloon payment at 10 years

Monthly payment $2703.54 (principal and interest)

Total monthly payments $227,097.36 (years 1-10)

Total 10-year balloon payment $447,847.36

Total amount paid $675,000

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Rehab costs $100,000-150,000

ARV $1,100,000

Refinance with traditional loan after 18 months